46 U.S. Code § 4306 - Federal preemption

Unless permitted by the Secretary under section
4305 of this title, a State or political subdivision of a State may not establish, continue in effect, or enforce a law or regulation establishing a recreational vessel or associated equipment performance or other safety standard or imposing a requirement for associated equipment (except insofar as the State or political subdivision may, in the absence of the Secretary’s disapproval, regulate the carrying or use of marine safety articles to meet uniquely hazardous conditions or circumstances within the State) that is not identical to a regulation prescribed under section
4302 of this title.

Section
4306 establishes the Federal preemption of recreational boating standards and requirements. A State or a political subdivision may not establish, continue, or enforce a law or regulation establishing a performance or other safety standard that is not identical to a Federal standard. The Secretary may grant an exemption to a State when the State requirement is one that is needed to meet uniquely hazardous conditions or circumstances within a State. This is to provide uniform standards without the imposition of excessive special requirements by individual States.